This invention relates generally to dock levelers. More particularly, the invention relates to lip structures that provide the final transition between a dock leveler or dock board and the interior of a truck trailer.
Dock levelers and dock boards are widely used to provide a transition between a loading dock and the interior of a truck trailer. Such devices enable fork lifts and similar vehicles to transit from a warehouse, factory or other loading dock area into a truck trailer and then back again. This simplifies the loading and unloading of trucks.
For a number of reasons, it is impractical to ensure that the bed of every truck trailer is kept at precisely the same height above ground at all times. This dimension changes with such factors as manufacturing variations, loadings, tire pressures, suspension sag etc. Accordingly, modern dock levelers function to accommodate variations in truck trailer height and to provide a ramp up or down as needed to form a smooth transition between the loading dock and the interior of the truck trailer.
Although dock levelers are generally heavy duty pieces of equipment manufactured from thick steel, the actual interface between the dock leveler and the interior of a truck trailer is preferably formed by a carefully shaped shelf or lip carried at the extreme forward end of the dock leveler. This helps provide a smooth transition between the dock leveler and the truck trailer interior that improves safety and comfort for the fork lift operator and helps simplify and speed the loading or unloading operation.
The simplest form of lip has been a "throw over" plate that was dropped into position over the juncture between the dock and the end of the truck trailer. Although effective, the throw over plate has serious drawbacks. In the first place, the throw over plate is an entirely separate unit that can be misplaced or lost. Additionally, it is often a heavy piece of metal that is difficult to maneuver and position without considerable body strength. Finally, proper positioning of the throw over plate depends substantially on the care and skill of the operator. Inattentive or indifferent concern on the part of the operator can result in an unsafe condition.
More advanced forms of lips include mechanisms located at the forward end of a dock leveler. Typically, a lip plate is hinged or otherwise pivotally mounted at the end of the dock leveler. To place the dock leveler in use, the dock leveler is first raised and the lip then pivoted outwardly. The dock leveler is then dropped until the lip comes to rest in the interior of the truck trailer. To provide adequate clearance for pivoting the lip, it is often necessary to raise the dock leveler well above the height needed to match the truck trailer height. To avoid potential pinch hazards created as the dock leveler is raised to such extreme levels, elaborate guard mechanisms are often employed along the sides of the dock leveler. Such mechanisms are intended to block any gaps between the sides of the dock leveler and the floor of the loading dock area to keep hands, feet and toes from getting caught therebetween. Although effective, such guards are often complicated telescoping or folding mechanisms that are difficult to construct and that increase the overall cost of the dock leveler substantially.